Size effects in thin films of superfluidHe3

We report the first identification of the phase of superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ in a geometry confined on the scale of the correlation length. For a wide range of pressures and temperatures at which the B phase is stable in bulk, the A phase occurs in thin films. The order-parameter structure is deduced by nuclear magnetic resonance. Simultaneous measurements of the superfluid density monitor the magnitude of the energy gap. We demonstrate that the boundary condition on the order parameter is tunable. Pair breaking is reduced dramatically at surfaces covered by adsorbed monolayers of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$.